( Source from the book
"Vietnam - The Helicopter War" by Philip D. Chinney
Copyright 1991)

Helicopter Organization in VietnamThere were four basic categories of the Army aviation units in
Vietnam. The first was the Airmobile Division and only two such units operated
in Vietnam; the 1st Cavalry Division which brought four heicopter battalions
with it from the United States and the 101st Airborne Division, the later
converting to Airmobile status whilst already in Vietnam in 1968. The second
category was the regular infantry division's organic aviation unit, which
comprised one aviation battalion of two companies and one Air Cavarly troop. One
such example is the 25th Infantry Division's organic 25th Aviation Battalion,
which arrived in Vietnam in 1966. The unit comprised 'A' and 'B' Company and 'D'
Troop, 3rd Squadron, 4th Cavalry. Infantry Divisions which brought their own
aviation battalions with them, included the 1st, 4th, 9th, 23rd (Americal),
25th, and the 101st.

The third category was the non-divisional aviation companies. As more
aviation companies were sent to Vietnam, aviation battalions were organized to
exercise control over them. The battalions in turn came under the control of
aviation groups. The number of aviation companies attached to a battalion would
vary, as would the number of battalions under the control of a group. In March
1966 the 1st Aviation Brigade was formed to exercise central control of these
non-divisional units and to ensure more effective use of resources, organization
and experience.

The fourth and final category covered the various smaller flights and
detachments, which served USMACV, USARV, the Signal, Engineer, Artillery,
Transport and other general support commands. Generally, smaller than an
aviation company and often consisting of only one or two Hueys, these units
operated a variety of aircraft, and eventually came under the control of the 1st
Aviation Brigade. It would be appropriate to mention that the Army also operated
fixed-wing companies and detachments in Vietnam, such as Surveillance, Utility
and Reconnaissance Airplane Companies.

* Note: The 9th Air Cavalry Brigade (Provisional) was formed in December 1970 by
the first Cavalry Division (Airmobile) to perform reconnaissance over a large
part of the Cambodian border area. It comprised the 1st Squadron, 9th Cavalry
(Reinforced) and the 3rd Squadron, 17th Cavalry, working with the Rangers of H
Company, 75th Infantry and the combat tracker dogs of the 62nd Infantry
Platoon.